1. Field of the Invention
This invention relates to visual inspection of the internal structure of large apparatus without dismantling by inserting a television probe into passages in the apparatus. In particular, the invention relates to devices for positioning the probe for viewing and includes a remotely controlled motorized carriage which carries the television probe through passages in apparatus such as a steam turbine and extends the probe for inspection of remote parts, such as the nozzle block and turbine blades.
2. Background Information
Typically large machines must be kept running to realize a return on investment, and in many instances, to provide a necessary continuous service. Hence, there has long been an interest in being able to inspect the internal structure of large machines without dismantling the apparatus, both for trouble shooting and for scheduling down time for preventative maintenance.
One such large machine is the steam turbine which drives an electrical generator to produce commercial power. Borescopes and, more recently, television probes have been used for this purpose. The television probes were originally developed for medical applications such as the remote inspection of internal passages in the human body. Very high resolution television cameras mounted on the ends of articulated probes have been developed for this purpose. Examples of such articulated probes, known as endoscopes, are disclosed in U.S. Pat. Nos. 3,557,780; 3,669,098; 4,700,693; 4,794,912; and 4,962,751.
While endoscopes with multiple bending axes have been developed for medical uses, they are not suitable for negotiating the long tortuous passages which lead to the critical parts such as the nozzle block and turbine blades inside a large steam turbine.
Remotely controlled carriages have been developed for inspecting the internal parts of machines such as turbine generators. U.S. Pat. No. 4,803,563 discloses a remotely controlled carriage for inspecting the stator of an electrical generator without removal of the rotor. This carriage is driven by several sets of wheels rectilinearly along the straight stator slots, and therefore does not require steering. A number of permanent magnets secure the carriage in the slots at all locations around the stator. The carriage carries a television camera for visual inspection of the stator as well as an eddy current detector. The camera is rather large and fixed on the carriage.
Commonly owned U.S. Pat. Nos. 4,889,000; 4,962,660 and 5,020,234 disclose additional carriages insertable in the stator slots of electric generators for performing various types of inspections. The carriages inserted in U.S. Pat. Nos. 4,962,660 and 5,020,234 mount a smaller television probe in a fixed position to observe the operation of an impact device and mechanical probe, respectively.
Commonly owned U.S. Pat. No. 4,811,091 discloses an inspection carriage which is remotely steerable through the stator ducts of a turbine generator. Separate motors drive wheels on each side of the carriage to effect steering. A television probe fixed on the carriage is aimed by maneuvering the entire carriage. The carriage is articulated for climbing over obstructions in the ducts, and also carries a number of permanent magnets which give it traction for climbing vertical walls of the metal ducts.
These known remotely controlled inspection devices are too large to reach the locations to be inspected in apparatus such as a steam turbine, and do not have the capability of maneuvering the television probe independently of the carriage to insert the probe into small openings, such as the spacing between turbine blades and other tights spots within a steam turbine.
There remains a need, therefore, for an improved device and technique for inspecting the internal structure of apparatus having internal passages without the need to dismantle the apparatus.
More specifically, there is a need for a device which can transport a video probe through the passages in the apparatus and extend the video probe into restricted passages to inspect selected internal features of the apparatus.
There is a related need for such a device for transporting the video probe which is small enough to maneuver in narrow passages of all orientations and can negotiate discontinuities in the passages.